It has long been a goal of telescope manufacturers to provide and for astronomers to have a telescope and control system which is easy to use by even the most unexperienced of observers. That is, the telescope should be easy to set up, should enable the observer to easily find the desired celestial object or objects in the sky and should provide a means whereby the desired object may be kept in view for a period of time for obervation thereof. To aid in achieving the desired goals, various telescope mounts have been developed. The most common mount is a tripod arrangement by which the telescope is supported for pivotal motion about a declination axis and an orthogonal right ascension axis. Initially, the telescope is set up such that the right ascension axis is directed toward the North Star (for observers in the Northern Hemisphere) or an imaginary southern polar point (for observers in the Southern Hemisphere).
An imaginary line drawn from the telescope to the North Star or southern polar point is commonly referred to as the polar axis. The description hereinafter set forth, while directed toward observatories in the northern hemisphere applies equally for observatories in the southern hemisphere by simply substituting the southern polar point for the North Star. To so align the right ascension axis with the North Star, i.e., with the polar axis, the typical method is to align the telescope field of view with its right ascension axis, sight the North Star and, while maintaining the sighting of the North Star, adjust the tripod legs until the telescope is adequately supported. As can be appreciated, the sighting of the North Star and maintaining such alignment while the legs are adjusted is a time consuming, frustrating and exerting task.
Once the right ascension axis (polar axis) has been established, the telescope may be pivoted about the right ascension axis and tilted upwardly and downwardly relative to the horizon about the declination axis to find or sight a selected object. Once found, a clock drive pivots the telescope about the right ascension axis at a rate to compensate for earth's rotation thereby keeping the object in view. When viewing planets or the moon, as opposed to stars, certain adjustments must be made to the clock drive to take into account not only the earth's rotation but the relative orbital motions between the earth and the planet or the moon.
To locate a selected object, the observer moves the telescope until the object comes into view. Accordingly, the observer must be knowledgeable to an extent to be able to identify the object from other celestial objects in the sky. To aid observers, star charts and indexes have been tabulated which, when the time, date, latitude and longitude of the telescope are known, give the location of objects in degrees, ascension and declination. Therefore, by referring to such charts or indexes the observer can locate by appropriately moving the telescope and observe the object with only small adjustments necessary.
As can be appreciated, the procedure for setting up the telescope, establishing the polar axis and finding a particular celestial object or objects requires skill, strength, and knowledge of the relative positions of the objects in the sky or an understanding of star charts or indexes. When it is desired to view a set of objects, each object of that set must be identified and sighted either with or without the use of the star chart or index. The foregoing has inhibited amateur astronomers from fully enjoying astronomy.
For large institutional telescopes, i.e., Palomar Observatory, Kitt Peak or the like, the telescopes are large so as to require DC motor drives engaging large gears to pivot in the right ascension and declination axis. Due to the cost to construct and operate such large telescopes, computer controls can be provided to control operation of these motors. For such observatories, the operator need input into the computer control the desired object, (i.e., its coordinates, in degrees right ascension or declination or some other key input data). The computer energizes the motors to properly position of the telescope to view the selected object. Position sensors (i.e. encoders) are provided to give a position feedback signal to the computer and to enable the computer to correctly position the telescope. A clock also provides input into the computer to enable the computer to properly position the telescope, the computer also perhaps providing the clock drive necessary to track the object. Since the latitude and longitude of the observatory is constant, the clock provides the time input and the operator inputs the date, the computer is enabled to find any selected object.
The DC motor drives and computer controls for the large telescopes are too expensive and cumbersome to be suitable for the smaller telescopes used by amateur astronomers. Further, for the smaller telescopes the DC motor type drives with encoder feedback would not provide the accuracy necessary. Accordingly, the desireability of computer control for amateur telescopes was heretofore thought impractical, too expensive, if not unfeasible.